Earth

1. Earth

2. Introduction • What did life look like when the first living organisms appeared 3 billion years ago? • What about during the age of the dinosaurs? • How can we be sure that dinosaurs really existed? • This section examines the origins of life, extinctions and the appearance of humans.

3. Fossils • The word FOSSIL describes; • all traces of life from geological periods • generally found in sediments and sedimentary rocks (ex. Limestone & sandstone) • the remains of animals, plants or humans • remains include; skeletons, shells, leaves and eggshells. • Fossils can also be traces of activity (footprints) • Fossilization= transformation of a living organism into a fossil

4. Major stages in the history of life on Earth • The Precambrian Era (4550 - 542 Ma) • The Paleozoic Era (542 - 251 Ma) • The Mesozoic Era (251 - 65.5 Ma) • The Cenozoic Era (65.5 Ma – present) (*** Ma = Million years ago***)

5. The Precambrian Era(4550 – 542 Ma) • The first era of geological time • The formation of the Earth and appearance of life • Began with the formation of the solar system • The first life forms appeared approx. 3 billion years ago • They were PROKARYOTES

6. The Precambrian Era (Cont’d) • Prokaryotes are bacteria consisting of a single cell with no nucleus • Later, bacteria capable of photosynthesis appeared , allowing oxygen to be released into the Earth’s atmosphere. Photosynthesis: A process used by plants and some types of bacteria to create organic matter from the water and CO2 found in the atmosphere, accompanied by the release of oxygen.

7. The Precambrian Era (Cont’d) • The first eukaryotic cells, which contained a nucleus appeared 2 to 1.4 billion years ago. • These more complex life forms consisting of several cells include worms, soft coral and jellyfish.

8. The Paleozoic Era (542-251 Ma) • Covers 300 million years in six periods. (Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian) Cambrian • Hot climate and shallow oceans were ideal for the development of new animal life forms. • Thousands of species of trilobites, marine arthropods that swam or crawled were developed.

9. Cambrian cont’d • Pikaia, small animal resembling an eel (5cm long) • The first animal with a vertebral column • The ancestors of reptiles, dinosaurs, birds and mammals, including humans Ordovician • During this period the first plants appeared Such as mosses and mushrooms.

10. Ordovician cont’d • At the end of this period the climate became so cold that almost half of the animal species disappeared • This was the first massive extinction. Silurian Period • Giant sea scorpions appeared as well as the first jawless fishes • Diversified quickly and gave rise to jawed fishes. (ancestors of sharks and rays)

11. Devonian Period • Terrestrial plants diversified quickly into tall trees • Devonian period ended with a series of events such as: • Increase in water temperature • Rise of CO2 levels • Glaciation • Responsible for the second massive extinction

12. Carboniferous Period • The arrival of the first conifers • These trees formed vast forests • The land was filled with scorpions, cockroaches, giant centipedes, and giant dragonflies • The first reptiles appeared, such as, snakes, turtles, lizards, and iguanas

13. Permian Period • Last period of Paleozoic era • Temperatures ranged between 0 & 40 degrees Celsius • Plants, amphibians and reptiles developed on the continent • Sea urchins lived in the water • Known for the largest extinction in the Earth’s history

14. Permian Period cont’d • Glaciations, intense volcanic activity triggering sulphuric-acid rain and the greenhouse effect and destruction of the ozone layer • These events were responsible for the third massive extinction • 96% of marine species and 75% of land species disappeared

15. The Mesozoic Era (251-65.5Ma) • Divided into three periods; the Triassic, the Jurassic, and the Cretaceous • The climate was warmer and less extreme than during the Paleozoic era. Triassic Period • 10 degrees C higher than today’s temperate seas, which allowed green algae to thrive • Dinosaurs first appeared and would go on to dominate the Mesozoic era

16. Triassic Period cont’d • Pteranodon was the first ancestor of birds • Some dinosaurs were herbivores such as the brachiosaurus • Some dinosaurs were carnivores such as the Tyrannosaurus rex. • The fourth massive extinction took place • 50% of fishes, sponges and corals disappeared due to meteorite impact and volcanic eruptions

17. Jurassic Period • Known as the age of the dinosaurs • The climate was stable and favored the development of marine and land fauna • The first birds and small mammals appeared along with flowering plants • At the end of this period, Pangea, the single continent began to break up

18. Cretaceous Period • Pangea divided into continents which eventually drifted to their current locations • The continental drift triggered major climate changes • The sea level was 200m higher than it is today • Flowering plants multiplied and bees flourished • Ended with fifth extinction caused by a meteorite impact in Northern Yucatan, Mexico • One of the main reasons dinosaurs disappeared

19. The Cenozoic Era (65.5 Ma – Today) • The Cenozoic era is divided into three periods: the Paleogene, Neogene, and Quaternary Paleogene Period • Mammals were small but kept developing • The first know large mammal was the dinocerate, it resembled a rhino • New groups emerged including, horses,whales, and the ancestors of elephants

20. Neogene Period • The creation of graminaceous plants (large family of plants that incl. wheat, rice, bamboo and sugar cane) • The land was home to giant armadillos, sabre-toothed tigers, and species related to modern day cats and dogs • Some of these species disappeared during the Quaternary period

21. Quaternary Period • On occasion polar ice covered a large part of the Northern Hemisphere • The climate alternated from warm to cold, this affected mammals which developed rapidly • The mammoth and woolly rhino appeared during cold periods • The hippo and elephant developed during the warm periods

22. Quaternary Period cont’dEvolution of the human species The Australopithecus/ Homo habilis • Coexisted with the most ancient human line along with Homo habilis 2.5 Ma • Homo habilis walked upright, had a human face, a large nose, prominent jaws and eyebrow ridge, and a low, sloped forehead • Its brain size was between 600-700cm3 (human brain size today = 1300-1500cm3) • First species to use tools, did not know how to use fire

23. Quaternary Period cont’dEvolution of the human species Homo erectus • Approx. 1.8Ma, homo habilis evolved to become homo erectus (“man who walks upright”) • Its brain size was 800-1000cm3 • It had developed a spoken language • Made the first stone tools with edges on both sides • Well organized camps demonstrated a developed social structure

24. Quaternary Period cont’dEvolution of the human species • Homo erectus made a discovery 400 000 years ago that would change the course of humankind: it learned to use fire • Homo erectus then slowly evolved into Neanderthal man Neanderthal man • Its robust body was adapted to the cold • Its brain was even larger than that of the modern day human

25. Quaternary Period cont’dEvolution of the human species • It made sophisticated tools to hunt lions and bears, also made traps to hunt elephant • Had burial sites and could be quite artistic • Cohabited with Homo sapiens, then disappeared between 40 000and 30 000yrs ago

26. Quaternary Period cont’dEvolution of the human species Homo sapiens • The “modern day human”, appeared between 300 000 and 100 000 yrs ago • Its brain size was approx 1500cm3 • First discovered in the Near East (Qafzeh cave in Galilee) • It began to populate Europe and gave rise to Cro-Magnon man, one of our most famous ancestors

27. Quaternary Period cont’dEvolution of the human species • Homo sapiens became sedentary and practiced agriculture • Developed artistic talents and made cave paintings of animals and humans • Invented writing, which marked the end of the prehistoric era and the beginning of the historic era

28. Recent Extinctions • Approx. 11 000 years ago, several animal species disappeared from North America • Mostly large mammals, such as; mammoth, the sabre-toothed tiger and the giant beaver • There were several causes: • Hunting and fires • The spread of disease by humans • Climate changes

29. Recent Extinctions cont’d • While the major extinctions may appear to have occurred suddenly, they took place over several thousands or millions of years • The current rate of extinction is 100x faster than the average rate tens of millions of years ago • No matter what happens, the survivors of the sixth extinction will take the place of the species that disappear, just as mammals and birds replaced the dinosaurs